package com.kpmg.datalake.common.utils;

import java.util.Map;

/**
 * @author Alex.zhao [alex.zhao@kpmg.com]
 * @since Created on azhao6 on 2018-08-20 21:27:29
 */
public class SqlParser {

  private SqlParser() {
  }

  public static String parse(String text, Map<String, Object> params) {
    return parse(text, params, "${", "}");
  }

  public static String parse(String text, Map<String, Object> params, String openToken,
      String closeToken) {
    int start = text.indexOf(openToken, 0);
    if (start == -1) {
      return text;
    }
    char[] src = text.toCharArray();
    int offset = 0;
    final StringBuilder builder = new StringBuilder();
    while (start > -1) {
      if (start > 0 && src[start - 1] == '\\') {
        // this open token is escaped. remove the backslash and continue.
        builder.append(src, offset, start - offset - 1).append(openToken);
        offset = start + openToken.length();
      } else {
        // found open token. let's search close token.
        StringBuilder expression = new StringBuilder();
        builder.append(src, offset, start - offset);
        offset = start + openToken.length();
        int end = text.indexOf(closeToken, offset);
        handEnd(end, offset, src, text, closeToken,
            expression);
        if (end == -1) {
          // close token was not found.
          builder.append(src, start, src.length - start);
          offset = src.length;
        } else {
          Object param = params.get(expression.toString());
          builder.append(param == null ? "" : param);
          offset = end + closeToken.length();
        }
      }
      start = text.indexOf(openToken, offset);
    }
    if (offset < src.length) {
      builder.append(src, offset, src.length - offset);
    }
    return builder.toString();
  }

  private static void handEnd(int end, int offset, char[] src, String text, String closeToken,
      StringBuilder expression) {
    while (end > -1) {
      if (end > offset && src[end - 1] == '\\') {
        // this close token is escaped. remove the backslash and continue.
        expression.append(src, offset, end - offset - 1).append(closeToken);
        offset = end + closeToken.length();
        end = text.indexOf(closeToken, offset);
      } else {
        expression.append(src, offset, end - offset);
        break;
      }
    }
  }
}
